1. Field of the Invention
The present invention relates to a surface mountable device that is surface mounted on a motherboard such as a printed circuit board by, for example, soldering, and more specifically, to a surface mountable device in which the appearance of the bonding condition with the motherboard can be visually inspected.
2. Description of the Related Art
FIGS. 16 to 19 show examples of the structure of known surface mount devices. FIG. 16 is a perspective view showing a state in which a surface mount device 30 including side electrodes 33 disposed at the side surface of the substrate is mounted on a motherboard 32 (a mount board for a device) by soldering. FIG. 17 is a cross-sectional view taken along imaginary cutting line B-B in FIG. 16. Land electrodes 34 of the motherboard 32 for mounting the surface mount device 30 are generally arranged so as to be exposed from the side surface of the surface mount device 30 toward the outside by a width a. Thus, the land electrodes 34 are intentionally exposed from the side surface toward the outside in order to form solder 35 having a certain thickness at the side surface of the surface mount device 30. This structure increases the peel strength of the surface mount device 30.
FIG. 18 is a perspective view showing a state in which a surface mount device 31 including terminal electrodes 37 disposed at the bottom surface of the substrate is mounted on a motherboard 32 by soldering. For example, as disclosed in Japanese Unexamined Patent Application Publication No. 8-250620 (hereinafter referred to as “Patent Document 1”), a surface mount device including external connection electrodes in a ball grid array (BGA) structure corresponds to such a surface mount device. FIG. 19 is a cross-sectional view taken along imaginary cutting line C-C in FIG. 18. Land electrodes 34 of the motherboard 32 for mounting the surface mount device 31 are generally disposed at the inside so as not to be exposed from the side surface of the surface mount device 31 to the outside. In this structure, solder 35 is not exposed from the side surface of the surface mount device 31 toward the outside, thereby improving the packaging density of the motherboard 32. Recently, downsizing has been highly desired, and the surface mount devices shown in FIG. 18 in which terminal electrodes are disposed at the bottom surface of the substrate has become desirable.
For both of these types of surface mount devices, such as electronic components, after the surface mount devices are mounted on a motherboard, the appearance is inspected to confirm the solderability. Regarding the surface mount device 30 shown in FIG. 16, the appearance can be checked by visual inspection 36 because the solder 35 is provided outside of the surface mount device 30. On the other hand, with the surface mount device 31 shown in FIG. 18, the appearance cannot be thoroughly checked by visual inspection because the solder 35 is provided in a narrow clearance between the surface mount device 31 and the motherboard 32. Consequently, Japanese Unexamined Patent Application Publication No. 10-170455 (hereinafter referred to as “Patent Document 2”) discloses a method for inspecting the appearance by X-ray transmission.
However, even if the method for inspecting the appearance described in Patent Document 2 can be applied to the surface mount device 31 shown in FIG. 18, the method cannot be easily applied to the actual manufacturing process in terms of the cost because a transmission apparatus required for the appearance inspection by X-ray transmission is expensive.